Method for arranging a busbar system and a busbar system

ABSTRACT

In order to make switchgear equipped with a busbar system for high voltages/current strengths less space-consuming, and to simplify the jointing and connection of the busbars and therewith also simplify manufacture and assembly of the busbar system, the busbars of the system have been given the form of tubes. A tubular cylindrical busbar is jointed/connected with the aid of a conductive contact element ( 9 ) in the form of a ring-shaped coil spring located between the insertion end ( 6 ) of one tube and an insertion end ( 7 ) of an adjacent tube. As the insertion end carrying the spring is inserted into a receiving end of an adjacent tube when joining two tubes together, the spring is compressed and remains compressed while exerting a pressure and holding force on the two tube ends. The voltage and current through tubular busbars that have been jointed with the aid of the springs are affected minimally by the springs, because each turn of the coil spring provides several points of contact with each tube end, therewith providing essentially loss-free electrical transmission.

The present invention relates to a method of connecting anddisconnecting the modules of air insulated switchgear, and a busbarsystem for enabling high voltages and/or high current strengths to beused in air insulated switchgear with a high degree of safety, forinstance.

DESCRIPTION OF THE BACKGROUND ART

Air insulated switchgear intended for high voltages≧1 Kv and highcurrent strengths are often equipped with flat busbars that have a highcopper content and preferably a rectangular cross-section. Thecross-sectional surface area of a busbar and its distance from anotherconductive material must be dimensioned in accordance with thevoltage/current strength levels so that losses will be small and therisk of flashover reduced. Thus, in high voltage plants of theswitchgear kind, a busbar system having a rectangular cross-section mayrequire a relatively large amount of space in order to prevent theoccurrence of flashover. The busbars are joined and connected by meansof screw/nut joints, therewith creating contact surfaces between thebusbars and respective jointing means. Conventional busbar systems aremost often assembled and fitted by mechanics or like artisans, and thework involved is relatively laborious and time-consuming. AS a result,the work necessitated in connecting and disconnecting switchgear modulesis complicated, time-consuming and dependent on the services of anartisan or mechanic.

SUMMARY OF THE INVENTION

With the intention of reducing the space requirements of air insulatedswitchgear having a busbar system for high voltages/high currentstrengths and simplifying jointing and connection of the busbar systemand therewith simplifying the manufacture and fitting of the system, thebusbars of the busbar system have been given the form of tubes which,when applicable, have welded/soldered thereto tubular connectors forconnecting the system to contact breaker connections. The insertion endof one busbar tube has fitted on its insertion end an electricallyconductive contact element in the form of an annular coil spring whichis received and affixed in the receiving end of another busbar tubeconfigured to this end, therewith enabling the tubular cylindricalbusbar to be easily joined/connected together. As the spring-carryinginsertion end of said busbar tube is inserted into the receiving end ofthe other tube, the spring is compressed and therewith exerts a pressureand holding force between the tubes while remaining in a compressedstate. The coupling and holding force exerted between the insertion endof the one tube and the receiving end of the other tube can be improvedby providing a groove in the inner surface of the said receiving end ofthe other tube, so that the spring is able to expand to some extent. Thespring provides a large number of contact points with each tube end,therewith providing an efficient tube coupling and an essentiallyloss-free contact for electrical transmission purposes. A contact whichis stable over a long period and with which the minimum of oxidationoccurs can be obtained by protecting the contact points from thesurrounding atmosphere with the aid of seals on both sides and byoptionally greasing the enclosed volume. The use of tubes in airinsulated switchgear enables the busbars to be disconnectedcabinet-wise/unit-wise and also enables coupling means in the maincurrent path to be removed without needing to loosen or remove fixedconnections in the busbar system. Thus, in the assembly of switchgeardifferent switchgear modules can be readily connected together bypushing the insertion ends of respective tubular busbars into thecorresponding receiving ends of juxtaposed tubular busbars.

According to another embodiment of the present invention, there is useda tubular jointing element which is mounted on the outer ends of thetubular busbars. The jointing element may have the form of a tubeprovided with an electrically conductive contact element in the form ofa ring-shaped coil spring fixed on the outer side of the jointingelement, one coil spring at each end. The tubular busbars are joinedtogether by pressing the spring-carrying jointing element into thetubular busbars to be joined together, therewith compressing thesprings, which remain compressed and exert a pressing and holding forcebetween the tubular busbars and the jointing element. The couplingstrength and retaining strength of the joint can be improved byproviding a groove on the inner surface of respective tubular busbars,so as to enable the springs to expand to some extent.

The jointing element may also have the form of a tube which includes anelectrically conductive contact element in the form of a ring-shapedcoil spring fixed on the inside of the jointing element, one coil springat each end. In this case, the tubular busbars are pressed into thejointing element, therewith compressing the springs.

The joints produced in accordance with the present invention give agreater degree of reliability than conventional bolt joints, becausethey eliminate the risk of human error involved with earlier used boltconnections.

In the case of a tubular busbar system in air insulated switchgearintended for high voltages and high current strengths, the spacingbetween respective busbars can be made smaller than the spacing betweenthe rectangular busbars of conventional busbar systems havingrectangular cross-section with the same quantity of material per unitlength, therewith obtaining switchgear with smaller outer dimensions. Asa result of the skin effect among other things, i.e. the phenomenon bywhich high frequency currents tend to be confined to the thin skin ofconductors, tubular busbars are able to conduct more current than ahomogenous busbar having the same cross-sectional surface area, at thesame time as the electrical power field becomes weaker around thebusbar. The “electrode” effect that is liable to be obtained withconventional busbars and result in flashover is not obtained with around busbar. The round shape is also retained in the joints whenpracticing the inventive jointing technique. Neither will soldering andwelding of copper tubes with the aid of present-day techniques result inweakenings or negatively effect the electrical conductivity; on thecontrary, the electrical resistance may be reduced in the region of theconnection by the solder/weld.

Cooling air can be circulated through the tubular busbars of thedescribed busbar system, either by forced circulation with the aid of afan, or by natural circulation with the aid of upwardly and downwardlyangled terminating means at both ends of the busbar system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates air insulated switchgear having a busbar systemcomprised of tubes in accordance with the invention.

FIG. 2 shows different views of an inventive tubular busbar forming partof a busbar system and having a tubular connector part welded thereon.

FIG. 3 illustrates in detail the connection, or jointing, of tubularbusbars provided with contact elements and forming part of a busbarsystem.

FIG. 4 illustrates in detail connected or jointed tubular busbarsprovided with contact elements and sealing elements and forming part ofa busbar system in accordance with the invention.

FIG. 5 illustrates the contact element of the FIG. 3 embodiment.

FIG. 6 illustrates alternative embodiments of a contact element.

FIG. 7 illustrates switchgear provided with a tubular busbar system inaccordance with the invention, and also shows flexible cooling tubesconnected to the busbars.

FIG. 8 illustrates the connection or jointing of tubular busbarsprovided with contact elements, sealing elements, and coupling meansaccording to a first embodiment and forming part of a busbar system inaccordance with the invention.

FIG. 9 illustrates the connection, or jointing of tube busbars providedwith contact elements and coupling or jointing means in accordance witha second embodiment and forming part of a busbar system in accordancewith the invention.

DESCRIPTION OF AN EXEMPLIFYING EMBODIMENT

Shown in FIG. 1 is an air insulated switchgear 1 which includes a busbarsystem comprised of cylindrical tubes 2 preferably having a high coppercontent, where the uppermost tubular busbars are connected at 3 betweenthe different switchgear units, wherein some of the protective plates ofthe switchgear have been omitted in FIG. 1 for the sake of illustration.In the illustrative systems of FIGS. 1 and 7 three switchgear units ofmodules are shown. In general terms, the system can be described ascomprising a plurality, n, of modules, wherein n is an integer and n≧2,each module i, wherein 1≦i≦n, comprising switchgear equipment, and aplurality of busbars protruding side by side through the module i forconnection with a consecutive module i+1. Thus, in the illustrativeexample of FIGS. 1 and 7, n=3. Tubular cross-pieces 4 for connectionwith circuit breaker connections, for instance, extend from the tubularbusbars. FIG. 2 illustrates in detail a tubular busbar which has weldedthereon a cross tube for connection to a circuit breaker connection forinstance. One end of the tubular busbar, the so-called insertion end 7is provided with grooves 5 for a contact element and a sealing elementrespectively. The other end of the busbar, the so-called receiving end6, may have a smooth inner surface in the illustrated case. FIGS. 3a andb illustrates in detail a receiving end 6 and an insertion end 7 of atubular busbar respectively, said insertion end 7 being provided with acircumferentially extending groove 8 and an electrically conductivecontact element affixed therein. FIG. 3c shows the contact-elementcarrying insertion end 7 partially inserted into the receiving end 6,with the contact element 9′ compressed. FIG. 3d is a schematiccross-sectional view of the contact element in said groove 8 prior toinsertion, 9, and after insertion, 9′, of an insertion end 6, and alsoillustrates the electrical contact points 10 in the groove on theinsertion end an in the inner wall of the receiving end.

Busbar systems that are constructed from tubular busbars can be cooled/ventilated by passing air, optionally cooled air, through the tubes,wherein one or more sealing elements 11 may be fitted onto the insertionend in grooves provided herefor, or a sealing element 11 may be fittedon the insertion end and an outer sealing element 13 may be fitted overthe connecting or jointing area. By efficiently sealing the joints, thespace within the tube system may be totally shielded from thesurrounding atmosphere, and the tubes may optionally be evacuated orfilled with a gaseous substance particularly adapted for the field ofuse. Sealing of the joints will also provide protection againstoxidation.

FIG. 4a is a schematic section view of the insertion end and receivingend of two jointed tubular busbars with a contact element 9 in thegroove 8 and two sealing elements, such as O-rings 11, provided one oneach side of the groove 8. FIG. 4b is a schematic section view of twomutually jointed tubular busbars with a contact element 9 provided inthe groove 8, a sealing element, such as an O-ring 12, fixed in agroove, and an outer protecting and sealing element, such as a shrinksleeve 13, fitted over the receiving and insertion ends of the tubes.

FIG. 8 is a schematic section view of two mutually jointed tubularbusbars 20. The joint has been accomplished with a tubular jointingmeans 22 which has contact elements 9 fitted in grooves at respectiveouter ends of the jointing means 22, and two sealing elements, such asO-rings 11, fixedly mounted in grooves on respective sides of thecontact elements 9 between the tubular busbars 20 and the jointing means22.

FIG. 9 is a schematic section view of two mutually jointed tubularbusbars 20. The joint has been accomplished with the aid of a tubularjointing means 24 which has contact elements 9 fitted in respectivegrooves on the inside of the jointing means 24 at respective outer endsthereof.

The use of the illustrated jointing means 22, 24 provides greaterflexibility when installing and disconnecting modules in and from an airinsulated switchgear, because problems relating to tolerances are lesspronounced when joining the tubular busbars together, for instance.

FIG. 5 illustrates an electrical contact element in the form of acircular and closed spirally wound spring intended for use in a busbarsystem. The spring may be made of a copper alloy, for instance berylliumcopper, optionally plated with silver. In order to enhance radialcompression of the contact element, the turns of the helix may beinclined to a greater or lesser extent. FIG. 6a illustrates anotherexample of a contact element whose helical turns have an alternativeinclination with greater deviation from the radial plane. The contactelement can be adapted for different fields of use, by changing thepitch and the number of turns of the contact element, said turnspreferably having an elliptical cross-section. FIG. 6b shows a contactelement having essentially straight turns.

FIG. 7 shows the manner in which switchgear 1 having a busbar systemcomprised of tubes 2 is connected to each tube for cooling of a flexibletube 14 or hose which functions to deliver gas, optionally cooled gas,to the tubular busbars. Depending on the field of use, the cooling gasmay be delivered with the aid of a fan, or may pass through the tubes bynatural ventilation. Cooling by natural ventilation can be achieved by a“chimney effect” in principle in accordance with FIG. 7.

What is claimed is:
 1. A busbar system for air insulated switchgear,characterized in that the busbar system is comprised of cylindricaltubular busbars (2), preferably having a high copper content; in thatthe tubular busbars have a busbar receiving end (6) and a busbarinsertion end (7) enabling the tubular busbars to be joined together byinserting the insertion end into the receiving end; and in that acontact element (9) is mounted between the receiving end (6) and theinsertion end (7) and functions to fix the tubular busbars together andestablish an electric contact therebetween; and in that an outerprotecting or sealing element is mounted over the join area of therespective receiving and insertion ends (6, 7) or mutually joinedtubular busbars, said contact element (9) being a round and closed coilspring.
 2. A busbar system according to claim 1, characterized in thatthe busbar insertion end (7) is provided with a circumferentiallyextending groove (8) in which the contact element (9) is affixed.
 3. Abusbar system according to claim 2, characterized in that the internalatmosphere of one of said tubular busbars or of several mutuallyconnected tubular busbars (2) is isolated from the outer atmospheresurrounding said one tubular busbar or busbars.
 4. A busbar systemaccording to claim 2, characterized in that one of said tubular busbarsor several mutually connected tubular busbars (2) is/are arranged to bethroughpassed by gas by natural ventilation for cooling the busbarsystem.
 5. A busbar system according to claim 1, characterized in thatthe internal atmosphere of one of said tubular busbars or of severalmutually connected tubular busbars (2) is isolated from the outeratmosphere surrounding said one tubular busbar or busbars.
 6. A busbarsystem according to claim 1, characterized in that one of said tubularbusbars or several mutually connected tubular busbars (2) is/arearranged to be throughpassed by gas by natural ventilation for coolingthe busbar system.
 7. A busbar system for air insulated switchgear,characterized in that the busbar system is comprised of cylindricaltubular busbars (2), preferably having a high copper content; in thatthe tubular busbars have a busbar receiving end (6) and a busbarinsertion end (7) enabling the tubular busbars to be joined together byinserting the insertion end into the receiving end; in that a contactelement (9) is mounted between the receiving end (6) and the insertionend (7) and functions to fix the tubular busbars together and establishan electric contact therebetween; and in that an outer protecting orsealing element is mounted over the join area of the respectivereceiving and insertion ends (6, 7) of mutually joined tubular busbars;and in that a sealing element (11) is seated between the receiving end(6) and the insertion end (7) and functions to effect a seal betweenmutually joined tubular busbars, the busbar insertion end (1) beingprovided with one or more grooves for affixing the sealing element (11).8. A busbar system according to claim 7, characterized in that theinternal atmosphere of one of said tubular busbars or of severalmutually connected tubular busbars (2) is isolated from the outeratmosphere surrounding said one tubular busbar or busbars.
 9. A busbarsystem according to claim 8, characterized in that one of said tubularbusbars or several mutually connected tubular busbars (2) is/arethroughpassed by a gas for cooling the busbar system.
 10. A busbarsystem according to claim 7, characterized in that one of said tubularbusbars or several mutually connected tubular busbars (2) is/arearranged to be throughpassed by gas by natural ventilation for coolingthe busbar system.
 11. A busbar system for air insulated switchgearcomprising tubes (20) for connection to one another by applying atubular jointing means (22; 24) to the outer ends of the tubes (20); andin that an electric contact element (9) is seated between each outer endof the tubes (20) and the jointing means (22; 24) so as to achievefixation and electrical contact between the tubes (20) when joining saidtubes together; and in that an outer protecting or sealing element ismounted over the join area of the tubular jointing means (22; 24) andthe outer ends of the tubes (20), the jointing means (22) having on theoutside of each outer end thereof a groove in which a respectiveelectric contact element (9) is affixed, and the outer diameter of thejointing means (22) being smaller than the inner diameter of the tubes(20).
 12. A busbar system according to claim 11, characterized by asealing element (11) seated between the tubes (20) and said jointingmeans (22;24) so as to establish a seal between said tubes when thetubes are connected together.
 13. A busbar system for air insulatedswitchgear comprising tubes (20) for connection to one another byapplying a tubular jointing means (22; 24) to the outer ends of thetubes (20); and in that an electric contact element (9) is seatedbetween each outer end of the tubes (20) and the jointing means (22; 24)so as to achieve fixation and electrical contact between the tubes (20)when joining said tubes together; and in that an outer protecting orsealing element is mounted over the join area of the tubular jointingmeans (22; 24) and the outer ends of the tubes (20), the jointing means(24) including on the inside thereof at each outer end of said jointingmeans a groove in which the electric contact element (9) is affixed, andthe inner diameter of the jointing means (24) being larger than theouter diameter of the tubes (20).
 14. A busbar system according to claim13, characterized by a sealing element (11) seated between the tubes(20) and said jointing means (22;24) so as to establish a seal betweensaid tubes when the tubes are connected together.
 15. A busbar systemaccording to claim 14, characterized in that the jointing means (22) hasprovided on its outer surface at least two grooves in which respectivesealing elements (11) are fixed.
 16. A busbar system according to claim14, characterized in that the jointing means (24) is provided on itsinner surface with at least two grooves in which respective sealingelements (11) are fixed.
 17. A method for erecting an air insulatedswitchgear comprising a plurality, n, of modules, wherein n is aninteger and n≧2, each module, i, wherein 1≦i≦n, comprising switchgearequipment, and a plurality of busbars protruding side by side throughsaid module i for connection with a consecutive module i+1, definingbetween each adjacent busbar a safety distance, wherein each busbar hasa tubular shape with an insertion end which is plug shaped, and areceiving end which is sleeve shaped, said method comprises the steps:to connect a module i and consecutive module i+1 by insertion of theplug shaped insertion ends of said busbars of said consecutive modulei+1 into the sleeve shaped receiving ends of said busbars of said modulei; and to repeat the above mentioned step for 1≦i≦n until all said nmodules are connected.
 18. A method for erecting an air insulatedswitchgear according to claim 17, characterized in that said method alsocomprises the step: to provide an electrically conductive contactelement between each insertion end and each receiving end of saidbusbars.
 19. A busbar system of an air insulated switchgear having aplurality, n, of modules, wherein n is an integer and n≧2, each module,i, wherein 1≦i≦n, comprising switchgear equipment, and a plurality ofbusbars protruding side by side through said module i for connectionwith a consecutive module i+1, defining between each adjacent busbar asafety distance, wherein each busbar has a tubular shape, therebycreating a smooth electric field permitting a narrower safety distancebetween adjacent busbars, wherein each busbar has an insertion end whichis plug shaped, and a receiving end which is sleeve shaped, wherein saidmodule i and said consecutive module i+1 are connected by insertion ofthe plug shaped insertion ends of said busbars of said consecutivemodule i+1 into the sleeve shaped receiving ends of said busbars of saidmodule i, wherein this is performed for all said n modules.
 20. A busbarsystem of an air insulated switchgear according to claim 19,characterized in that an electrically conductive contact element isdisposed between each insertion end and each receiving end of saidbusbars.
 21. A busbar system according to claim 20, characterized by anouter protecting or sealing element, in the form of a shrink sleeve(13), mounted over the join area of the respective receiving andinsertion ends (6, 7) of mutually joined said tubular busbars.
 22. Abusbar system according to claim 20, characterized by a sealing element(11) seated between the receiving end (6) and the insertion end (7) andfunctioning to effect a seal between mutually joined tubular busbars.23. A busbar system according to claim 19, characterized in that theinternal atmosphere of one or of several mutually connected said tubularbusbars (2) is isolated from the outer atmosphere surrounding said oneor several busbars.
 24. A busbar system according to claim 23,characterized in that said one or several mutually connected saidtubular busbars (2) is/are throughpassed by a gas for cooling the busbarsystem.
 25. A busbar system according to claim 19, characterized in thatsaid one or several mutually connected said tubular busbars (2) arearranged to be throughpassed by natural ventilation for cooling thebusbar system.
 26. A busbar system of an air insulated switchgear havinga plurality, n, of modules, wherein n is an integer and n≧2, eachmodule, i, wherein 1≦i≦n, comprising switchgear equipment, and aplurality of busbars protruding side by side through said module i forconnection with a consecutive module i+1, defining between each adjacentbusbar a safety distance, wherein each busbar has a tubular shape,thereby creating a smooth electric field permitting a narrower safetydistance between adjacent busbars, wherein each busbar has an insertionend which is plug shaped, and a receiving end which is sleeve shaped,wherein said module i and said consecutive module i+1 are connected byinsertion of the plug shaped insertion ends of said busbars of saidconsecutive module i+1 into the sleeve shaped receiving ends of saidbusbars of said module i, wherein this is performed for all said nmodules, wherein an electrically conductive contact element is disposedbetween each insertion end and each receiving end of said busbars, andwherein the contact element (9) is a round and closed coil spring.
 27. Abusbar system according to claim 26, characterized in that the busbarinsertion end (7) is provided with a circumferentially extending grove(8) in which the contact element (9) is affixed.
 28. A busbar system ofan air insulated switchgear having a plurality, n, of modules, wherein nis an integer and n≧2, each module, i, wherein 1≦i≦n, comprisingswitchgear equipment, and a plurality of busbars protruding side by sidethrough said module i for connection with a consecutive module i+1,defining between each adjacent busbar a safety distance, wherein eachbusbar has a tubular shape, thereby creating a smooth electric fieldpermitting a narrower safety distance between adjacent busbars, whereineach busbar has an insertion end which is plug shaped, and a receivingend which is sleeve shaped, wherein said module i and said consecutivemodule i+1 are connected by insertion of the plug shaped insertion endsof said busbars of said consecutive module i+1 into the sleeve shapedreceiving ends of said busbars of said module i, wherein this isperformed for all said n modules, wherein an electrically conductivecontact element is disposed between each insertion end and eachreceiving end of said busbars, wherein a sealing element (11) is seatedbetween the receiving end (6) and the insertion end (7) and functions toeffect a seal between mutually joined tubular busbars, and wherein thebusbar insertion end (1) is provided with one or more grooves foraffixing the sealing element (11).